<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
</head>
<body>
<form>
    用户名：<input type="text">
    按钮：<input type="button">
</form>

<script type="text/javascript" src="http://libs.baidu.com/jquery/2.0.0/jquery.js"></script>
<script src="https://cdn.bootcss.com/jquery/1.12.4/jquery.min.js"></script>
</body>
<script type="text/javascript">
    function test() {
        alert(123);
    }
    $(function () {
        alert(122);
    });
</script>
</html>